Missing productOfferingGroups attributes values for parent BPO's in TmaExportController

I'm using TmaExportsController to fetch productOfferings in b2ctelcostore.

I am particularly interested in the offeringGroup attribute for bundled product offerings.

The issue is that the offeringGroup is missing for parent BPO's.

I debugged the code and found that the model's retrieved have the relevant data(offeringGroup) till the service layer.

But, when it comes to facade layer the data(offeringGroup) seems to be missing in the same list of models.